首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1289篇
  免费   109篇
  国内免费   280篇
安全科学   100篇
废物处理   93篇
环保管理   103篇
综合类   614篇
基础理论   248篇
污染及防治   214篇
评价与监测   271篇
社会与环境   23篇
灾害及防治   12篇
  2024年   9篇
  2023年   11篇
  2022年   27篇
  2021年   31篇
  2020年   33篇
  2019年   44篇
  2018年   35篇
  2017年   40篇
  2016年   72篇
  2015年   68篇
  2014年   71篇
  2013年   159篇
  2012年   104篇
  2011年   133篇
  2010年   85篇
  2009年   85篇
  2008年   88篇
  2007年   90篇
  2006年   87篇
  2005年   59篇
  2004年   58篇
  2003年   58篇
  2002年   39篇
  2001年   29篇
  2000年   30篇
  1999年   22篇
  1998年   29篇
  1997年   25篇
  1996年   20篇
  1995年   17篇
  1994年   9篇
  1993年   4篇
  1991年   3篇
  1989年   1篇
  1987年   1篇
  1986年   1篇
  1983年   1篇
排序方式: 共有1678条查询结果,搜索用时 320 毫秒
701.
Chemically mediated communication is common in spiders but has been poorly studied in burrowing tarantulas. This study aimed to determine whether chemical cues influence the behaviour of females of Brachypelma vagans, a Mexican species of tarantula, during encounters with previously inhabited burrows or with extracts from the silk of conspecific females. In laboratory choice tests, female tarantulas entered a burrow that had previously been inhabited by a conspecific female significantly more frequently than a burrow that had never been inhabited. The identity of the previous inhabitant also affected the number of spiders that chose to enter a burrow. Spiders were quicker to choose and enter a burrow previously inhabited by themselves than a burrow previously inhabited by a conspecific or a burrow that had not been previously inhabited. Hexane, methanol and dichloromethane extracts of conspecific silk elicited different responses from female tarantulas when extracts were placed on filter paper disks at one end of an experimental arena with a control filter paper disk, on to which the corresponding solvent alone had been pipetted, placed on the other end of the arena. Spiders showed the strongest responses to hexane extracts of silk, with a significant preference to move towards the hexane extract and a significantly greater period of time spent in proximity to the hexane extract compared to the control disk. Overall and in contrast to expectations, tarantulas were most strongly attracted to the cues left by other conspecific females. As encounters between B. vagans females usually lead to aggression and mortality of one of the participants, we conclude that chemical cues are not signals that are deliberately released by burrow-inhabiting females but may inadvertently escape and cannot be easily suppressed.  相似文献   
702.
以广西环江地区某尾矿库3个区域的尾矿样品为研究对象,在化学成分和矿物成分分析的基础上,运用Dold七步分级化学提取法,研究了Zn,Cd,Pb,As,Sb和Ni 6种重金属的赋存形态特征,并分析了其潜在迁移能力。结果表明,3个区域的尾矿样品均为碳酸盐型金属硫化物尾矿,样品中Zn和Pb的质量浓度较高(分别达4 119.9 mg/kg和3 375.1 mg/kg),Cd和Ni的质量浓度相对较低,As和Sb的质量浓度差别较大(可达191.5 mg/kg和86.5 mg/kg)。形态分析结果表明,Zn和As的迁移性较强,且具有一定的环境风险,Pb,Cd,Sb和Ni相对较稳定。  相似文献   
703.
The treatment of wastewaters is crucial to maintain the ecological status of receiving waters, and thereby guarantee the protection of aquatic life and human health. Wastewater quality evaluation is conventionally based on physicochemical parameters, but increasing attention has been paid to integrate physicochemical and biological data. Nevertheless, the regulatory use of fish in biological testing methods has been subject to various ethical and cost concerns, and in vitro cell-based assays have thus become an important topic of interest. Hence, the present study intends: (a) to evaluate the efficiency of two different sample pre-concentration techniques (lyophilisation and solid phase extraction) to assess the toxicity of municipal effluents on rat cardiomyoblast H9c2(2-1) cells, and (b) maximizing the use of the effluent sample collected, to estimate the environmental condition of the receiving environment. The gathered results demonstrate that the H9c2(2-1) sulforhodamine B-based assay is an appropriate in vitro method to assess biological effluent toxicity, and the best results were attained by lyophilising the sample as pre-treatment. Due to its response, the H9c2(2-1) cell line might be a possible alternative in vitro model for fish lethal testing to assess the toxicity of municipal effluents. The physicochemical status of the sample suggests a high potential for eutrophication, and iron exceeded the permissible level for wastewater discharge, possibly due to the addition of ferric chloride for wastewater treatment. In general, the levels of carbamazepine and sulfamethoxazole are higher than those reported for other countries, and both surpassed the aquatic protective values for long-term exposure.  相似文献   
704.
以中国各行业SO2、NOx和烟粉尘的排放数据为基础,利用假设抽取法和投入产出价格模型,计算了各行业的需求排放、产出排放和净转移量,模拟了不同情景下重点行业减排后对整体行业需求排放的影响,并计算了重点减排行业污染成本内部化造成的价格传导影响系数.结果显示,2014年电力热力燃气供应业、非金属矿制品业和金属矿采选及冶炼延压业这3个重点行业大气污染物净转出量最大;在这3个行业同时减排15%的情景下,SO2、NOx和烟粉尘这3种污染物的减排量可以分别达到中国“十三五”节能减排目标的62.12%、72.65%和67.11%;电力热力燃气供应业作为大气污染物减排影响最大的行业,如果将其污染成本内部化,其生产产品的价格会对其余行业造成不同程度的影响,其中,对水生产和供应业、金属制品业产品、金属矿采选及冶炼延压业和非金属矿制品业的价格影响较大,总价格传导影响系数分别为0.272、0.151、0.148和0.131.因此,建立合理的大气污染物减排成本分摊机制一方面可以补贴基础转出行业的治理成本,另一方面可以通过价格机制激励其他行业提高技术水平,减少对电力等基础工业产品的需求.  相似文献   
705.
The geochemical characteristics of arsenic in the soil of the Western Hunan mining area of P.R. China were systematically studied. The results show that the strata of Western Hunan are rich in arsenic and that Western Hunan is a geochemically abnormal region for arsenic. The experimental study on speciation in the strata also indicates that the speciation of arsenic in the Neoproterozoic-Cambrian strata are mainly easily transferred speciation (exchangeable, carbonate-bound, sulfides-bound), which are approaching or exceed 60%. Arsenic content in the main soil of Western Hunan is in the range of 8.8–22.8 μg g−1, the mean value is 16.1 μg g−1, which is larger than the arsenic background value of Hunan soil. The distribution of rock with high arsenic content or high easily transferred arsenic speciation is consistent with the distribution of high arsenic content soil. In the mining region, part soils and river/brook waters were polluted by mine tailings and mining/smelting waste water. The arsenic content in polluted paddy soils and river/brook water is 46.26–496.19 μg g−1, 0.3–16.5 mgL−1, respectively. The positive abnormality and pollution of arsenic in the soil and water affects the arsenic content of the crop and the inhabitants’ health.  相似文献   
706.
There are many established extraction techniques regularly used in the isolation and analysis of PAHs and similar organic compounds from various phases. These include Soxhlet or ultrasonic extractions from solids, and liquid-liquid or solid-phase extraction from aqueous samples. However, these methods have some inherent disadvantages; most require large volumes of organic solvents, they can be time consuming and many involve multi-step processes that always present the risk of the loss of some analytes (Zhang et al., 1994). Solid-phase micro-extraction (SPME) is a relatively new technique that has been used with much success in the analysis of a variety of compounds including PAHs. Experiments are being carried out to determine the optimum range of conditions for the extraction of a range of PAHs. Parameters under investigation include temperature, equilibration time, salinity and compound concentration. Presented here are some preliminary experiments into the applicability of SPME for PAH analysis. Further work will investigate the reproducibility of the technique, limits of detection and matrix effects. When an optimised method has been developed the technique will be used in investigations into PAH profiles in sediment cores.  相似文献   
707.
正辛醇萃取苯酚稀溶液的特性研究   总被引:9,自引:0,他引:9  
林屹  秦炜  戴猷元 《环境化学》2003,22(1):48-52
为探索工业含酚废水处理的适宜萃取剂,进行了正辛醇萃取苯酚稀溶液的实验研究,测定了不同pH值和苯酚初始浓度条件下的萃取平衡数据,萃残液CODCr值,分析了萃残液中CODCr值的来源。综合考虑萃取剂的萃取能力和产生的CODCr值,提出了酸性和中性溶液为正辛醇处理苯酚废水的适宜操作条件。以正辛醇为萃取剂对工业含酚废水进行了错流萃取实验,论证了其应用的可行性。  相似文献   
708.
协同-络合萃取法回收含酚废水中的酚类   总被引:8,自引:0,他引:8  
葛宜掌  金红 《环境化学》1996,15(2):112-117
在现有的各种回收处理高浓度含酚废水的方法中,溶剂萃取法最为有效.但现有常用脱酚萃取剂分别存在着萃取效能低等诸多缺点,萃残液中一般尚存有几十至几百mg·l~(-1)的酚类,本文提出了协同-络合萃取法,并按该法原理研制了HC-1—HC-4四类新型协同-络合萃取剂.其中HC-3和HC-4对苯酚稀溶液的萃取平衡常数分别为K_((?)C-3)=612.4和K_((?)C-4)=483.7,单级萃取可将两组中高浓度的含酚废水中酚浓度降至10mg·l~(-1)以厂,脱酚率>99%.该法为一步脱酚达标提供了可能性.  相似文献   
709.
固相萃取法提取净化生物检材中三类农药的实验研究   总被引:19,自引:0,他引:19  
孙静  刘耀 《环境化学》1995,14(3):221-225
本文以常见的六种有机磷类、四种氨基甲酸脂类和五种拟种虫菊酯类农药为对象,研究了用国产GDX-403或C18固相小柱同时提取净化环境样品和生物检材中三种类型的农药,分别采用GC/FPD,GC/NPD和GC/ECD三种特征性气相色谱法进行分析鉴定,为系统分析有机农药提供了一套快速、简便的固相提取方法。  相似文献   
710.
地菍果实红色素的提取及其稳定性   总被引:8,自引:1,他引:8  
从地Nian(Melastona dodecandrum Lour)果实中提取出天然红色素,并对其理化性质进行了研究。结果表明,该色素为花青素类色素,对光、热的耐受性较好;耐氧化性,还原性及维生素C较差,受试的五种金属离子Fe^3 ,Cu^2 ,Mn^2 ,Mg^2 ,Zn^2 对色素的稳定性影响不大;食盐、蔗糖和苯甲酸钠亦无显著影响。该色素可作为新型天然食用色素加以开发利用,图2表10参5。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号